WO2010052980A1 - Optical film - Google Patents

Abstract

An optical film having excellent transparency and brittleness.  The optical film is characterized by containing an acrylic resin (A) and a cellulose ester resin (B) at a mass ratio of from 95:5 to 30:70.  The acrylic resin (A) has a weight average molecular weight (Mw) of not less than 110,000 but not more than 1,000,000.  The cellulose ester resin (B) has a weight average molecular weight (Mw) of not less than 75,000 but not more than 280,000, a total degree of substitution (T) of acyl groups of not less than 2.0 but not more than 3.0, and a degree of substitution of acyl groups having 3-7 carbon atoms of not less than 1.2 but not more than 3.0.  The optical film is also characterized by having the following relations. (1) average haze value ≤ 0.0150 × d (2) maximum haze value ≤ 0.0180 × d (In the relations, d represents the film thickness (μm) of the optical film.)

Description

Optical film

The present invention relates to an optical film suitable for optical applications having excellent transparency and brittleness.

An acrylic film typified by a polymethylmethacrylate film has been expected as an optical film because of its high transmittance in the visible light region, low intrinsic birefringence, and a small photoelastic coefficient.

However, acrylic films are prone to cracking, and their inferior brittleness has hindered their use.

As a countermeasure against cracking, a technique for adding a toughness improving agent to an acrylic film has been proposed (Patent Document 1).

Also known is a method of imparting flexibility by adding elastic particles to a specific acrylic film and further heat-treating (Patent Document 2).

A technique of mixing a flexible resin having a glass transition temperature of 10 ° C. or lower instead of elastic particles has also been proposed (Patent Document 3).

Since the method of Patent Document 1 was originally applied to an acrylic film that is prone to cracking, it was difficult to establish production conditions and lacked versatility.

The method of Patent Document 2 has a problem that the time required for the heat treatment is very long and the transparency of the produced acrylic film is inferior.

The method of Patent Document 3 is effective for a specific acrylic resin having a lactone ring structure, and since it is premised on melt casting, the transparency does not exceed the level of Patent Document 2. It was.

Patent Document 4 proposes manufacturing an acrylic film containing a cellulose ester resin by melt casting. However, transparency is not always satisfactory by simple melt mixing, and brittleness is not sufficient.

Japanese Patent Laid-Open No. 5-119217 WO2005 / 105918 JP 2007-100044 A JP 2008-88417 A

In the present invention, an object is to provide an optical film having excellent transparency and brittleness.

The above-mentioned problem of the present invention is solved by the following means.

1. The acrylic resin (A) and the cellulose ester resin (B) are in a mass ratio of 95: 5 to 30:70, and the weight average molecular weight Mw of the acrylic resin (A) is 110,000 to 1000000, and the cellulose ester resin (B ) Having a weight average molecular weight Mw of 75,000 or more and 280000 or less, a total substitution degree (T) of the acyl group of 2.0 or more and 3.0 or less, and a substitution degree of the acyl group of 3 or more and 7 or less carbon atoms is 1. An optical film characterized by being 2 or more and 3.0 or less and having the following relationship.

(1) Haze average value ≦ 0.0150 × d
(2) Haze maximum value ≦ 0.0180 × d
(D represents the film thickness μm of the optical film.)
2. The optical film as described in 1 above, wherein 2.1.0 ≦ haze maximum value / haze average value ≦ 1.1.

3. 3. The optical film as described in 1 or 2 above, wherein the width of the optical film is 1.8 to 4 m.

According to the present invention, an optical film having excellent transparency and brittleness can be obtained.

It is the figure which showed typically the dope preparation process, casting process, and drying process of the solution casting film forming method used for this invention.

<Optical film>
The optical film of the present invention is an acrylic film containing an acrylic resin (A) and a cellulose ester resin (B) in a mass ratio of 95: 5 to 30:70, and the weight average molecular weight Mw of the acrylic resin (A). Is 110,000 or more and 1000000 or less, the weight average molecular weight Mw of the cellulose ester resin (B) is 75000 or more and 280000 or less, and the total substitution degree (T) of the acyl group is 2.0 or more and 3.0 or less, Is an optical film characterized in that the degree of substitution of acyl groups of 3 or more and 7 or less is 1.2 or more and 3.0 or less and has the following relationship.

(1) Haze average value ≦ 0.0150 × d
(2) Haze maximum value ≦ 0.0180 × d
(D represents the film thickness μm of the optical film.)
Furthermore, 1.0 ≦ haze maximum value / haze average value ≦ 1.1.

The above haze relationship is such that the haze of the acrylic film of the present invention is uniform over the entire surface, that is, it is excellent in transparency, and when used as an optical film of a liquid crystal display device, image unevenness hardly occurs. It means that.

The average haze value and maximum haze value are obtained as follows.

A square side of 3.5 cm square is cut out at intervals of 5 cm from one end in the TD direction to the other end. Further, at an arbitrary position, 50 or more square sides of 3.5 cm square are cut out in the MD direction at intervals of 5 cm in the MD direction. The haze of all the square-side films produced above was measured using a haze meter NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), and an average value and a maximum value were obtained.
<Acrylic resin (A)>
The acrylic resin (A) used in the present invention includes a methacrylic resin. The resin is preferably composed of 50 to 100% by mass of methyl methacrylate units and 0 to 50% by mass of other monomer units copolymerizable therewith.

Examples of other copolymerizable monomers include alkyl methacrylates having 2 to 18 alkyl carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, alkyl acrylates such as acrylic acid and methacrylic acid. Saturated acids, maleic acids, fumaric acids, divalent carboxylic acids containing unsaturated groups such as itaconic acid, aromatic vinyl compounds such as styrene, α-methylstyrene, and nucleus-substituted styrene, α, β- such as acrylonitrile, methacrylonitrile, etc. Examples thereof include unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, and glutaric anhydride, and these can be used alone or in combination of two or more.

Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

The acrylic resin (A) used in the acrylic film of the present invention has a weight average molecular weight (Mw) of 110000 to 1000000, preferably 150,000 from the viewpoint of mechanical strength as a film and fluidity when producing the film. ~ 400000.

The large weight average molecular weight of the acrylic resin (A) is one of the important elements of the present invention that exhibits the excellent transparency and brittleness of the acrylic film of the present invention.

The weight average molecular weight of the acrylic resin (A) of the present invention can be measured by gel permeation chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

The production method of the acrylic resin (A) in the present invention is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used. Here, as a polymerization initiator, a normal peroxide can be used, an azo type can be used, and a redox type can also be used.

The polymerization temperature may be 30 to 100 ° C. for suspension or emulsion polymerization, and 80 to 160 ° C. for bulk or solution polymerization. Furthermore, in order to control the reduced viscosity of the produced copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

By using this molecular weight, both transparency and brittleness can be achieved.

A commercially available thing can also be used as an acrylic resin (A) of this invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. .
<Cellulose ester resin (B)>
The acrylic film of the present invention preferably contains a cellulose ester resin (B) from the viewpoint of transparency, particularly when improved with brittleness and heat resistance, and when mixed with the acrylic resin (A). The cellulose ester resin (B) has a total substitution degree (T) of acyl groups of 2.0 to 3.0 and a substitution degree of acyl groups of 3 to 7 carbon atoms of 1.2 to 3.0. Is preferred. That is, the cellulose ester resin (B) is a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used, and a propionyl group is particularly preferably used. .

When the total substitution degree of the acyl group of the cellulose ester resin (B) is less than 2.0, that is, when the residual degree of the hydroxyl groups at the 2, 3, and 6 positions of the cellulose ester molecule is more than 1.0, the acrylic ester The resin (A) is not sufficiently compatible with the haze.

In addition, even when the total substitution degree of the acyl group is 2.0 or more, if the substitution degree of the acyl group having 3 to 7 carbon atoms is less than 1.2, still sufficient compatibility cannot be obtained, Brittleness will decrease. For example, even when the total substitution degree of the acyl group is 2.0 or more, the substitution degree of the acyl group having 2 carbon atoms, that is, the acetyl group is high, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1. When it is less than 2, the compatibility is lowered and the haze is increased. Even when the total substitution degree of the acyl group is 2.0 or more, the substitution degree of the acyl group having 8 or more carbon atoms is high, and the substitution degree of the acyl group having 3 to 7 carbon atoms is less than 1.2. In such a case, the brittleness is lowered and desired characteristics cannot be obtained.

In the cellulose ester resin (B) of the present invention, the total substitution degree (T) is 2.0 to 3.0, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 to 3. If it is 0.0, there is no problem, but the total degree of substitution of acyl groups other than those having 3 to 7 carbon atoms, that is, acetyl groups or acyl groups having 8 or more carbon atoms, is preferably 1.3 or less.

In the present application, the “acyl group” is meant to include those further having a substituent. However, the carbon number of the acyl group includes a substituent of the acyl group.

When the cellulose ester resin (B) has an aromatic acyl group as a substituent, the number of substituents X substituted on the aromatic ring is preferably 0 to 5. Also in this case, it is necessary to pay attention so that the degree of substitution of the acyl group having 3 to 7 carbon atoms including the substituent is 1.2 to 3.0.

For example, since the benzyl group has 7 carbon atoms, when it has a substituent containing carbon, the benzyl group has 8 or more carbon atoms and is not included in the acyl group having 3 to 7 carbon atoms. Become.

Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

In the cellulose ester resin (B), a structure having at least one kind of a substituted or unsubstituted aliphatic acyl group having 3 to 7 carbon atoms is used as a structure used in the cellulose resin of the present invention.

The substitution degree of the cellulose ester resin (B) of the present invention is such that the total substitution degree (T) of the acyl group is 2.00 to 3.00, the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 to 3 .0.

Further, it is preferable that the total substitution degree of acyl groups other than an acyl group having 3 to 7 carbon atoms, that is, an acetyl group and an acyl group having 8 or more carbon atoms is 1.3 or less.

The cellulose ester resin (B) of the present invention is preferably at least one selected from cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate, particularly cellulose acetate. Propionate and cellulose propionate are more preferable.

Among these, particularly preferable cellulose ester resins (B) are cellulose acetate propionate and cellulose acetate butyrate, and those having an acyl group having 3 or 4 carbon atoms as a substituent are preferable.

The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

Incidentally, the substitution degree of the acetyl group and the substitution degree of other acyl groups were determined by the method prescribed in ASTM-D817-96.

The weight average molecular weight (Mw) of the cellulose ester resin (B) of the present invention is 75,000 or more, particularly from the viewpoint of improving compatibility with the acrylic resin (A) and brittleness, and is preferably in the range of 75,000 to 300,000. More preferably, it is within the range of 100,000 to 240,000, particularly preferably 160000 to 240000.
<Compatible state>
In the acrylic film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are preferably contained in a compatible state at a mass ratio of 100: 0 to 30:70.

It is preferably 95: 5 to 50:50, and more preferably 90:10 to 60:40.

In the acrylic film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) must be contained in a compatible state. The physical properties and quality required for an acrylic film are achieved by supplementing each other by dissolving different resins.

Whether the acrylic resin (A) and the cellulose ester resin (B) are in a compatible state is determined by the glass transition temperature Tg.

When both resins are simply mixed, there are two glass transition temperatures for each resin because there is a glass transition temperature for each resin. However, when both resins are compatible, each glass has its own glass transition temperature. The temperature disappears and becomes one glass transition temperature, which becomes the glass transition temperature of the compatible resin.

The glass transition temperature T _g1 , ₂ of this compatible mixture is approximated by the Gordon-Taylor equation (M. Gordon and JS Taylor, 2 J. of Applied Chem. 493-500 (1952)). It is known that it can be done.

T _g1 , ₂ = (w ₁ T _g1 + Kw ₂ T _g2 ) / (w ₁ + Kw ₂ )
[Where w ₁ and w ₂ are mass fractions of component 1 (acrylic resin (A)) and 2 (cellulose ester resin (B)); T _g1 and T _g2 are component 1 And T _g1 , ₂ is the glass transition temperature of the mixture of components 1 and 2; K is a constant related to the free volume of the two resins. ]
The acrylic resin (A) and the cellulose ester resin (B) are each preferably an amorphous resin, and either one may be a crystalline polymer or a partially crystalline polymer. In the present invention, the acrylic resin (A) and the cellulose ester resin (B) are preferably compatible with each other to become an amorphous resin.

The mixed resin obtained by polymerizing the precursor of acrylic resin (A) such as monomer, dimer or oligomer with cellulose ester resin (B) undergoes graft polymerization, crosslinking reaction or cyclization reaction. In many cases, it does not dissolve in a solvent or cannot be melted by heating, and does not correspond to the resin contained in the compatible state of the present invention.

The total mass of the acrylic resin (A) and the cellulose ester resin (B) in the acrylic film of the present invention is preferably 55% by mass or more of the acrylic film, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

When using a resin other than the acrylic resin (A) and the cellulose ester resin (B), it is preferable to adjust the addition amount within a range that does not impair the function of the acrylic film of the present invention.

Examples thereof include acrylic particles (C), polystyrene, polyvinyl acetate, polyolefin, and polycarbonate.
<Acrylic particles (C)>
The acrylic particles (C) of the present invention are characterized by existing in the form of particles in the acrylic film containing the acrylic resin (A).

Here, for example, a PTFE membrane having a pore diameter smaller than the average particle diameter of the acrylic particles (C) when a predetermined amount of the prepared acrylic film is collected, dissolved in a solvent, stirred, and sufficiently dissolved and dispersed. It is preferable that the weight of the insoluble matter filtered and collected using a filter is 90% by mass or more of the acrylic particles (C) added to the acrylic film.

The acrylic particles (C) used in the present invention are preferably acrylic particles (C) having a layer structure of two or more layers, and particularly preferably the following multilayered acrylic granular composite.

The multilayer structure acrylic granular composite is formed by laminating an innermost hard layer polymer, a cross-linked soft layer polymer exhibiting rubber elasticity, and an outermost hard layer polymer from the center to the outer periphery. This refers to a particulate acrylic polymer having a structure.

Preferred examples of the multilayer structure acrylic granular composite used in the acrylic resin composition of the present invention include the following. (A) Monomer comprising 80 to 98.9% by weight of methyl methacrylate, 1 to 20% by weight of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, and 0.01 to 0.3% by weight of polyfunctional grafting agent (B) 75 to 98.5% by mass of an alkyl acrylate having 4 to 8 carbon atoms in the presence of the innermost hard layer polymer in the presence of the innermost hard layer polymer, A crosslinked soft layer polymer obtained by polymerizing a monomer mixture comprising 0.01 to 5% by mass of a multifunctional crosslinking agent and 0.5 to 5% by mass of a multifunctional grafting agent; (c) the innermost hard In the presence of a polymer comprising a layer and a crosslinked soft layer, a monomer mixture comprising 80 to 99% by mass of methyl methacrylate and 1 to 20% by mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is polymerized. Outermost hard layer weight And the obtained three-layer structure polymer is an innermost hard layer polymer (a) 5 to 40% by mass, a soft layer polymer (b) 30 to 60% by mass, and An outermost hard layer polymer (c) comprising 20 to 50% by mass, having an insoluble part when fractionated with acetone, and an acrylic granular composite having a methyl ethyl ketone swelling degree of 1.5 to 4.0 at the insoluble part .

As disclosed in Japanese Patent Publication No. 60-17406 or Japanese Patent Publication No. 3-39095, not only the composition and particle diameter of each layer of the multilayered acrylic granular composite are defined, but also the multilayered acrylic granular composite. By setting the tensile modulus of the body and the swelling degree of methyl ethyl ketone in the acetone-insoluble part within a specific range, it is possible to realize a further sufficient balance between impact resistance and stress whitening resistance.

Here, the innermost hard layer polymer (a) constituting the multilayer structure acrylic granular composite is 80 to 98.9% by mass of methyl methacrylate and 1 to 20 mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group. % And a monomer mixture consisting of 0.01 to 0.3% by mass of a polyfunctional grafting agent is preferred.

Here, examples of the alkyl acrylate having 1 to 8 carbon atoms in the alkyl group include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like. And n-butyl acrylate are preferably used.

Examples of the polyfunctional grafting agent include polyfunctional monomers having different polymerizable functional groups, such as allyl esters of acrylic acid, methacrylic acid, maleic acid, and fumaric acid, and allyl methacrylate is preferably used. .

The polyfunctional grafting agent is used to chemically bond the innermost hard layer polymer and the soft layer polymer, and the ratio used during the innermost hard layer polymerization is 0.01 to 0.3% by mass. .

The crosslinked soft layer polymer (b) constituting the acrylic granular composite is an alkyl acrylate having from 9 to 8 carbon atoms having an alkyl group of 1 to 8 in the presence of the innermost hard layer polymer (a). What is obtained by polymerizing a monomer mixture consisting of 10% by mass, 0.01 to 5% by mass of a multifunctional crosslinking agent and 0.5 to 5% by mass of a multifunctional grafting agent is preferred.

Here, n-butyl acrylate or 2-ethylhexyl acrylate is preferably used as the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group.

In addition to these polymerizable monomers, it is possible to copolymerize 25% by mass or less of other monofunctional monomers capable of copolymerization.

Examples of other monofunctional monomers that can be copolymerized include styrene and substituted styrene derivatives. As the ratio of the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group and styrene increases, the glass transition temperature of the produced polymer (b) decreases as the former increases, that is, it can be softened.

On the other hand, from the viewpoint of the transparency of the resin assembly, the refractive index of the soft layer polymer (b) at room temperature is set to the innermost hard layer polymer (a), the outermost hard layer polymer (c), and the hard heat. It is more advantageous to make it closer to the plastic acrylic resin (A), and the ratio between the two is selected in consideration of these.

For example, in applications where the coating layer thickness is small, it is not always necessary to copolymerize styrene.

As the polyfunctional grafting agent, those mentioned in the section of the innermost layer hard polymer (a) can be used. The polyfunctional grafting agent used here is used to chemically bond the soft layer polymer (b) and the outermost hard layer polymer (c), and the proportion used during the innermost hard layer polymerization is impact resistance. From the viewpoint of the effect of imparting properties, 0.5 to 5% by mass is preferable.

As the polyfunctional crosslinking agent, generally known crosslinking agents such as divinyl compounds, diallyl compounds, diacrylic compounds, dimethacrylic compounds and the like can be used, but polyethylene glycol diacrylate (molecular weight 200 to 600) is preferably used.

The polyfunctional cross-linking agent used here is used to generate a cross-linked structure during the polymerization of the soft layer (b) and to exhibit the effect of imparting impact resistance. However, if the above-mentioned polyfunctional grafting agent is used during the polymerization of the soft layer, the polyfunctional crosslinking agent is not an essential component because the crosslinked structure of the soft layer (b) is generated to some extent. Is preferably 0.01 to 5% by weight from the viewpoint of imparting impact resistance.

The outermost hard layer polymer (c) constituting the multi-layer structure acrylic granular composite has a methyl methacrylate of 80 to 99 mass in the presence of the innermost hard layer polymer (a) and the soft layer polymer (b). % And a monomer mixture comprising 1 to 20% by mass of an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is preferred.

Here, as the acrylic alkylate, those described above are used, but methyl acrylate and ethyl acrylate are preferably used. The proportion of the alkyl acrylate unit in the outermost hard layer (c) is preferably 1 to 20% by mass.

Also, when the outermost hard layer (c) is polymerized, an alkyl mercaptan or the like can be used as a chain transfer agent to adjust the molecular weight for the purpose of improving the compatibility with the acrylic resin (A).

In particular, it is preferable to provide the outermost hard layer with a gradient such that the molecular weight gradually decreases from the inside toward the outside in order to improve the balance between elongation and impact resistance. As a specific method, the monomer mixture for forming the outermost hard layer is divided into two or more, and the molecular weight is increased from the inside to the outside by a method of sequentially increasing the amount of chain transfer agent to be added each time. It is possible to make it smaller.

The molecular weight formed at this time can also be examined by polymerizing the monomer mixture used each time under the same conditions, and measuring the molecular weight of the obtained polymer.

The particle diameter (diameter) of the acrylic granular composite which is a multilayer structure polymer preferably used in the present invention is not particularly limited, but is preferably 10 nm or more and 1000 nm or less, and more preferably 20 nm or more. , More preferably 500 nm or less, and most preferably 50 nm or more and 400 nm or less.

In the acrylic granular composite that is a multilayer structure polymer preferably used in the present invention, the mass ratio of the core and the shell is not particularly limited, but when the entire multilayer structure polymer is 100 parts by mass, The core layer is preferably 50 parts by mass or more and 90 parts by mass or less, and more preferably 60 parts by mass or more and 80 parts by mass or less.

In addition, specific examples of acrylic particles that are graft copolymers preferably used as acrylic particles (C) preferably used in the present invention include unsaturated carboxylic acid ester-based monomers in the presence of a rubbery polymer. A graft copolymer obtained by copolymerizing a monomer mixture of a polymer, an unsaturated carboxylic acid monomer, an aromatic vinyl monomer, and, if necessary, other vinyl monomers copolymerizable therewith. A polymer is mentioned.

Although there is no restriction | limiting in particular in the rubbery polymer used for the acrylic particle (C) which is a graft copolymer, Diene type rubber, acrylic type rubber, ethylene type rubber, etc. can be used. Specific examples include polybutadiene, styrene-butadiene copolymer, block copolymer of styrene-butadiene, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer. , Butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-butadiene copolymer, ethylene-isoprene copolymer, and ethylene-acrylic acid Examples thereof include a methyl copolymer. These rubbery polymers can be used alone or in a mixture of two or more.

Also, it is preferable that the acrylic resin (A) and the acrylic particles (C) have similar refractive indexes because the transparency of the acrylic film of the present invention can be obtained.

Specifically, the difference in refractive index between the acrylic particles (C) and the acrylic resin (A) is preferably 0.05 or less, more preferably 0.02 or less, and particularly preferably 0.01 or less.

In order to satisfy such a refractive index condition, a method of adjusting the monomer unit composition ratio of the acrylic resin (A), or the composition of the rubbery polymer or monomer used in the acrylic particles (C) The difference in refractive index can be reduced by a method of adjusting the ratio, and an acrylic film having excellent transparency can be obtained.

In addition, the refractive index difference here means that the acrylic film of the present invention is sufficiently dissolved in a solvent in which the acrylic resin (A) is soluble to obtain a cloudy solution, and this is subjected to an operation such as centrifugation. After separating the solvent-soluble part and the insoluble part and purifying the soluble part (acrylic resin (A)) and the insoluble part (acrylic particles), the difference in the measured refractive index (23 ° C., measurement wavelength: 550 nm) Indicates.

In the present invention, the acrylic resin (A) is mixed with the acrylic particles (C) by adding a solution in which the acrylic particles are dispersed in advance to a solution (dope solution) in which the acrylic resin (A) is dissolved. A method such as in-line addition of a solution or a solution obtained by dissolving and mixing acrylic particles (C) and other optional additives can be used.

As the acrylic particles (C) of the present invention, commercially available ones can be used. For example, METABRENE W-341 (C2), Chemisnow MR-2G (C3), MS-300X (C4) (manufactured by Mitsubishi Rayon Co., Ltd.) "Kane Ace" manufactured by Kaneken Chemical Co., Ltd., "Paraloid" manufactured by Kureha Chemical Industry Co., Ltd., "Acryloid" manufactured by Rohm and Haas Co., Ltd. Parapet SA ″ and the like can be mentioned, and these can be used alone or in combination of two or more.

The acrylic film of the present invention preferably contains 0.1 to 5% by mass of acrylic particles (C) based on the total mass of the resin constituting the film.
<Other additives>
The acrylic film of the present invention can contain an ultraviolet absorber, a retardation control agent, a matting agent, and an antioxidant as other additives.

<Ultraviolet absorber>
Moreover, in this invention, a ultraviolet absorber can also be used individually or in combination.

Conventionally known ultraviolet absorbers are not particularly limited. For example, salicylic acid ultraviolet absorbers (phenyl salicylate, p-tert-butyl salicylate, etc.) or benzophenone ultraviolet absorbers (2,4-dihydroxybenzophenone, 2,2). '-Dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, etc.), benzotriazole UV absorption Agents (2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) ) -5-Chlorobenzotriazole, 2- ( '-Hydroxy-3', 5'-di-tert-amyl-phenyl) benzotriazole, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α , Α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole, etc.), cyanoacrylate UV absorber (2′-ethylhexyl-2) -Cyano-3,3-diphenyl acrylate, ethyl-2-cyano-3- (3 ', 4'-methylenedioxyphenyl) -acrylate, etc.), triazine ultraviolet absorbers, or JP-A No. 58-185777, And compounds described in JP-A-59-149350, nickel complex compounds, inorganic powders, and the like.

Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to. In addition, since the transition from the thin coating layer to the substrate layer is particularly small and hardly precipitates on the surface of the laminate, the amount of contained UV absorber is maintained for a long time, and the durability of the weather resistance improvement effect is excellent. From the point of view, it is preferable.

Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] Such as til] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine A hybrid system having both structures can be mentioned, and these can be used alone or in combination of two or more.

Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

As the conventionally known ultraviolet absorber used together with the ultraviolet absorber of the present invention, a benzotriazole ultraviolet absorber and a benzophenone ultraviolet absorber that are highly transparent and excellent in preventing the deterioration of the polarizing plate and the liquid crystal element are preferable. Particularly preferred are benzotriazole-based UV absorbers with less unnecessary coloration.

In the present invention, a conventionally known ultraviolet absorbing polymer can also be used. The conventionally known UV-absorbing polymer is not particularly limited, and examples thereof include a polymer obtained by homopolymerizing RUVA-93 (manufactured by Otsuka Chemical) and a polymer obtained by copolymerizing RUVA-93 with other monomers. .

Specifically, PUVA-30M obtained by copolymerizing RUVA-93 and methyl methacrylate in a ratio (mass ratio) of 3: 7, and PUVA-50M copolymerized in a ratio of 5: 5 (mass ratio). It is done.
(Phase difference control agent)
In the present invention, as the retardation control agent, compounds described in JP-A No. 2002-296421 and various ester plasticizers can be used. Hereinafter, preferred ester compounds will be described in detail.

In the present invention, among various compounds described later, a compound having a structure in which aromatic rings are arranged in a plane when added as an additive and stretched is preferable.

For this reason, a compound in which an aromatic ring is contained as a block in the main chain or at the end is preferred.

<Polyester polyol>
The polyester polyol used in the present invention includes a dehydration condensation reaction between a glycol having an average carbon number of 2 to 3.5 and a dibasic acid having an average carbon number of 4 to 5.5, or the glycol. It is preferably one produced by a conventional method by addition of a dibasic anhydride having an average carbon number of 4 to 5.5 and a dehydration condensation reaction.

《Glycol》
Examples of the glycol used in the polyester polyol include ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propanediol, 1,4-butylene glycol, and neopentyl. Glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, and the like. These may be used alone or in combination of two or more. For example, ethylene glycol or a mixture of ethylene glycol and diethylene glycol Is particularly preferably used.

In addition, regarding the glycol described above, the average carbon number of the glycol is preferably in the range of 2 to 3.5 from the viewpoint of production of polyester polyol, compatibility with cellulose, transparency, and the like.

When a mixture of ethylene glycol and diethylene glycol is used as the glycol, the ethylene glycol / diethylene glycol molar ratio is preferably 25 to 100/75 to 0, and for cellulose esters having excellent compatibility with cellulose esters. A modifier can be obtained. Further, it is more preferably 25 to 40/75 to 60, and 60 to 95/40 to 5. By adjusting to such a range, the crystallinity and melting point of the polyester polyol are close to those of conventional ones. Productivity is also improved.

《Dibasic acid》
Next, examples of the dibasic acid constituting the polyester polyol used in the present invention include succinic acid, glutaric acid, adipic acid, and sebacic acid.

These can be used alone or in combination of two or more. For example, succinic acid or a mixture of succinic acid and terephthalic acid is particularly preferably used.

Regarding the dibasic acid described above, the average number of carbon atoms of the dibasic acid is preferably in the range of 4 to 5.5 from the viewpoint of production of polyester polyol, compatibility with cellulose, transparency, and the like. .

When a mixture of succinic acid and terephthalic acid is used as the dibasic acid, the succinic acid / terephthalic acid molar ratio is preferably 25 to 100/75 to 0, and has excellent compatibility with the cellulose ester. A cellulose ester modifier can be obtained.

Further, it is more preferably 25 to 40/75 to 60, and 60 to 95/40 to 5. By adjusting to such a range, the crystallinity and melting point of the polyester polyol are close to those of conventional ones. Productivity is also improved.

The glycol and dibasic acid constituting the polyester polyol used in the present invention include combinations other than the above, but the total of the average number of carbon atoms of the glycol and the average number of carbon atoms of the dibasic acid is 6-7. A combination of .5 is preferred.

The polyester polyol obtained from the glycol and the dibasic acid may have a number average molecular weight in the range of 1,000 to 200,000, more preferably a hydroxyl-terminated polyester having a number average molecular weight of 1200 to 1000. Those having a molecular weight of ˜4000 are particularly preferably used.

By using a polyester polyol having a number average molecular weight in such a range, a phase difference control agent (a modifier for cellulose ester) excellent in compatibility with the cellulose ester can be obtained by a solid phase reaction.

In obtaining the effects of the present invention, it is preferable from the viewpoint of retardation development, compatibility, moisture permeability and the like that the polyester polyol having the number average molecular weight of 1000 or more is contained in the film in an amount of 2 to 30% by mass. More preferably, it is 10 to 20% by mass.

Actually, the content of the polymer in the film depends on the type of polymer and the weight average molecular weight, and the performance such as dimensional stability, retentivity, and transmittance is within the range where dope, web, and phase separation does not occur after film formation. It is decided accordingly.

On the other hand, the content of the carboxyl group terminal in the polyester polyol used in the present invention is preferably 1/20 or less of the number of hydroxyl groups from the viewpoint of the effect of the present invention. It is more preferable to stop at 40 or less.

In the production of the above-described polyester polyol, conventionally known esterification catalysts such as metal organic acid salts or metal chelate compounds such as titanium, zinc, lead and zirconium, or antimony oxide can be used.

As such an esterification catalyst, for example, tetraisopropyl titanate, tetrabutyl titanate and the like are preferably used, and 0.0005 to 0.005 per 100 parts by mass in total of glycol (a) and dibasic acid (b) used. 02 parts by weight are preferably used.

Polyester polyol polycondensation is carried out by conventional methods.

For example, a direct reaction between the dibasic acid and glycol, the dibasic acid or an alkyl ester thereof, for example, a polyesterification reaction or transesterification reaction between a dibasic acid methyl ester and a glycol, or a hot melt condensation method Alternatively, it can be easily synthesized by any method of dehydrohalogenation reaction between acid chlorides of these acids and glycols, but polyester polyols whose number average molecular weight is not so large are preferably by direct reaction.

The polyester polyol having a high distribution on the low molecular weight side has a very good compatibility with the cellulose ester, and after forming the film, a moisture permeability is small and a cellulose ester film having a high transparency can be obtained.

The conventional method can be used as the molecular weight adjustment method without any particular limitation. For example, although depending on the polymerization conditions, the amount of these monovalent compounds can be controlled by a method of blocking the molecular ends with a monovalent acid or monovalent alcohol. In this case, a monovalent acid is preferable from the viewpoint of polymer stability.

For example, acetic acid, propionic acid, butyric acid, pivalic acid, benzoic acid and the like can be mentioned, but during the polycondensation reaction, such monovalent acid is not removed from the system but stopped and removed from the reaction system. Those which are easy to be distilled off when being removed from the system are selected, but these may be mixed and used.

In the case of direct reaction, the number average molecular weight can also be adjusted by measuring the timing of stopping the reaction according to the amount of water distilled off during the reaction. In addition, it can be adjusted by biasing the number of moles of glycol or dibasic acid to be charged or by controlling the reaction temperature.

<Aromatic terminal ester plasticizer>
As the retardation control agent of the present invention, an aromatic terminal ester plasticizer represented by the following general formula (I) can be used.

Formula (I) B- (GA) nGB
(Wherein B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In the general formula (I), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

Examples of the benzene monocarboxylic acid component of the aromatic terminal ester plasticizer of the present invention include, for example, benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propyl There exist benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., and these can be used as 1 type, or 2 or more types of mixtures, respectively.

Examples of the alkylene glycol component having 2 to 12 carbon atoms of the aromatic terminal ester plasticizer include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, and 1,3-butanediol. 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1 , 3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1,3-hexanediol , 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc., and these glycols are used as one kind or a mixture of two or more kinds Is done.

Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and the like. Or it can be used as a mixture of two or more.

Examples of the aryl glycol component having 6 to 12 carbon atoms of the aromatic terminal ester include hydroquinone, resorcin, bisphenol A, bisphenol F, and bisphenol. These glycols are used as one kind or a mixture of two or more kinds. Can be used.

Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal ester of the present invention include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are each used as one or a mixture of two or more.

Examples of the aryl dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, 1,5 naphthalenedicarboxylic acid, 1,4 naphthalenedicarboxylic acid and the like.

The number average molecular weight of the aromatic terminal ester plasticizer is preferably 300 to 2000, and more preferably 500 to 1500. The acid value is preferably 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

<< Acid value and hydroxyl value of aromatic terminal ester >>
“Acid value” refers to the number of milligrams of potassium hydroxide necessary to neutralize the acid (carboxyl group present at the molecular terminal) contained in 1 g of a sample. The acid value and the hydroxyl value are measured according to JIS K0070.

Hereinafter, specific compounds of the aromatic terminal ester plasticizer of the present invention will be shown, but the present invention is not limited thereto.

The content of the aromatic terminal ester plasticizer of the present invention is preferably 1 to 20% by mass, particularly preferably 3 to 11% by mass in the cellulose ester film.

<Polyhydric alcohol ester>
In the present invention, a polyhydric alcohol ester plasticizer can be further used as the retardation control agent.

The polyhydric alcohol ester used in the present invention is preferably an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

The polyhydric alcohol used in the present invention is represented by the following general formula (1).

Formula (1) R1- (OH) _n
In the formula, R1 represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic or phenolic hydroxyl group.

Examples of preferable polyhydric alcohols include the following.

Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol.

Of these, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

The monocarboxylic acid used in the polyhydric alcohol ester of the present invention is not particularly limited, and known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid and the like can be used.

Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferable in terms of improving moisture permeability and retention. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used.

More preferably, it has 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms. The use of acetic acid is preferred because the compatibility with the cellulose ester is increased, and it is also preferred to use a mixture of acetic acid and another monocarboxylic acid.

Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid , Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, Examples thereof include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

Examples of preferable alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, and derivatives thereof.

Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. In particular, benzoic acid is preferred.

The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750.

A larger molecular weight is preferable because it is less likely to evaporate, and a smaller one is preferable in terms of moisture permeability and compatibility with cellulose ester.

The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

The specific compounds of polyhydric alcohol esters are shown below.

<Sugar ester compound>
The retardation control agent of the present invention is preferably an acrylic film containing a sugar ester compound obtained by esterifying a hydroxyl group of a sugar compound in which 1 to 12 at least one structure selected from a furanose structure and a pyranose structure is bonded.

Examples of the sugar compound of the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose, etc., particularly those having both a furanose structure and a pyranose structure. preferable.

The ester compound is a monosaccharide (α-glucose, β-fructose) benzoate, or a monosaccharide represented by the following general formula (A): —OR ₁₂ , —OR ₁₅ , —OR ₂₂ , —OR ₂₅ A benzoic acid ester of a polysaccharide of m + n = 2 to 12 produced by dehydration condensation at two or more arbitrary positions is preferable.

The sugar ester compound of the present invention is one in which part or all of the hydroxyl groups of the sugar compound are esterified or a mixture thereof.

The benzoic acid in the above general formula may further have a substituent, for example, an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group have a substituent. You may have.

Specific examples of the esterified compound of the present invention will be given below, but the present invention is not limited thereto.

The acrylic film of the present invention preferably contains a sugar ester compound in an amount of 1 to 30% by mass of the total resin constituting the acrylic film in order to suppress the fluctuation of the retardation value and stabilize the display quality.

The sugar ester compound of the present invention is commercially available as Monopet SB (Daiichi Kogyo Seiyaku Co., Ltd.).

<Other phase difference control agents>
As the phase difference controlling agent of the present invention, those containing bisphenol A in the molecule are also preferred. A compound in which ethylene oxide or propylene oxide is added to both ends of bisphenol A can be used.

For example, BP series such as New Paul BP-2P, BP-3P, BP-23P, BP-5P, BPE-20 (F), BPE-20NK, BPE-20T, BPE-40, BPE-60, BPE-100, There are BPE series (manufactured by Sanyo Chemical Co., Ltd.) such as BPE-180, and BPX series (manufactured by Adeka Co., Ltd.) such as Adeka Polyether BPX-11, BPX-33, BPX-55.

Diallyl bisphenol A, dimethallyl bisphenol A, tetrabromobisphenol A in which bisphenol A is substituted with bromine, oligomers and polymers obtained by polymerizing this, bisphenol A bis (diphenyl phosphate) substituted with diphenyl phosphate, etc. Can be used.

Polycarbonate obtained by polymerizing bisphenol A, polyarylate obtained by polymerizing bisphenol A with a dibasic acid such as terephthalic acid, and an epoxy oligomer or polymer polymerized with an epoxy-containing monomer can also be used.

Modiper CL130D or L440-G obtained by graft polymerization of bisphenol A and styrene or styrene acrylic can also be used.

The acrylic film of the present invention can contain two or more retardation control agents. In this case, by optimizing the combination, elution of the phase difference controlling agent can be reduced.

The reason is not clear, but the amount of addition per one type can be reduced and elution is suppressed by the interaction between the two phase difference control agents and the acrylic resin (A) -containing composition. Seem.

<Antioxidant>
In this invention, what is generally known can be used as an antioxidant.

In particular, lactone, sulfur, phenol, double bond, hindered amine and phosphorus compounds can be preferably used.

For example, those including those commercially available from Ciba Japan under the trade names “IrgafosXP40” and “IrgafosXP60” are preferable.

The phenolic compound preferably has a 2,6-dialkylphenol structure. For example, trade names of Ciba Japan Co., Ltd., “Irganox 1076”, “Irganox 1010”, and ADEKA “ADEKA STAB AO-50” And those commercially available.

The phosphorus compounds are, for example, from Sumitomo Chemical Co., Ltd., “Sumizer GP”, from ADEKA Co., Ltd., “ADK STAB PEP-24G”, “ADK STAB PEP-36” and “ADK STAB 3010”, from Ciba Japan Co., Ltd. “IRGAFOS P-EPQ”, commercially available from Sakai Chemical Industry Co., Ltd. under the trade name “GSY-P101” is preferable.

The above-mentioned hindered amine compounds are preferably those commercially available from Ciba Japan Co., Ltd. under the trade names of “Tinuvin 144” and “Tinvin 770” and from ADEKA Co., Ltd. “ADK STAB LA-52”.

The above sulfur compounds are preferably those commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer TPL-R” and “Sumilizer TP-D”.

The above-mentioned double bond compound is preferably commercially available from Sumitomo Chemical Co., Ltd. under the trade names of “Sumilizer GM” and “Sumilizer GS”.

Furthermore, it is possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid scavenger.

The amount of these antioxidants and the like to be added is appropriately determined in accordance with the process for recycling and use, but generally 0.05 to 20% by mass, preferably with respect to the resin as the main raw material of the film Is added in the range of 0.1 to 1% by mass.

These antioxidants can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind. For example, the combined use of lactone, phosphorus, phenol and double bond compounds is preferred.

<Matting agent>
The acrylic film of the present invention preferably contains fine particles as a matting agent.

As fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated silicic acid. Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate. Further, fine particles of an organic compound can also be preferably used.

Examples of organic compounds include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene resin, silicone resin, polycarbonate resin, benzoguanamine resin, melamine resin Also, pulverized and classified products of organic polymer compounds such as polyolefin-based powders, polyester-based resins, polyamide-based resins, polyimide-based resins, polyfluorinated ethylene-based resins, and starches.

Alternatively, a polymer compound synthesized by a suspension polymerization method, a polymer compound made spherical by a spray dry method or a dispersion method, or an inorganic compound can be used.

Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

The average primary particle size of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm.

These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable.

The content of these fine particles in the film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a polarizing plate protective film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). it can.

Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.).

Examples of the polymer include silicone resin, fluororesin and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120 and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the polarizing plate protective film low. In the polarizing plate protective film used in the present invention, it is preferable that the dynamic friction coefficient of at least one surface is 0.2 to 1.0.

Various additives may be batch-added to the dope that is a solution before film formation, or an additive solution may be separately prepared and added in-line.

Particularly, it is preferable to add a part or all of the fine particles in-line in order to reduce the load on the filter medium.

In order to perform in-line addition and mixing in the present invention, for example, an in-line mixer such as a static mixer (manufactured by Toray Engineering), SWJ (Toray static type in-tube mixer Hi-Mixer) or the like is preferably used.

<Other additives>
In the acrylic film of this invention, in order to improve the fluidity | liquidity and softness | flexibility of a composition, it is also possible to use a plasticizer together. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

For phosphate plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenylbiphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate and the like can be used.

Of these, polyester-based and phthalate-based plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

In particular, when adipic acid, phthalic acid, or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

The ester plasticizer may be any of ester, oligoester and polyester types, and the molecular weight is preferably in the range of 100 to 10000, but preferably in the range of 600 to 3000, the plasticizing effect is large.

Also, the viscosity of the plasticizer has a correlation with the molecular structure and molecular weight, but in the case of an adipic acid plasticizer, the range of 200 to 5000 mPa · s (25 ° C.) is preferable because of compatibility and plasticization efficiency. Furthermore, some polyester plasticizers may be used in combination.

The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the composition containing the acrylic resin (A). If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use. These plasticizers may be used alone or in combination of two or more.

Furthermore, various antioxidants can be added to the acrylic resin (A) used in the acrylic film of the present invention in order to improve the thermal decomposability and thermal coloring during molding. It is also possible to add an antistatic agent to impart antistatic performance to the acrylic film.

As the acrylic resin (A) composition of the present invention, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphates, halogen-containing condensed phosphonates, halogen-containing phosphites, and the like.

Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.
<Film formation of acrylic film>
The preferable example of the manufacturing method by the solution casting film forming method of the acrylic film of this invention is demonstrated.

(Organic solvent)
An organic solvent useful for forming a dope when the acrylic film of the present invention is produced by a solution casting method is a mixed solvent containing solvents A and B.

A dope composition is prepared by dissolving at least 15 to 45 mass% in total of acrylic resin (A) and cellulose ester resin (B) in this mixed solvent.

1) Dissolution step Dissolution is performed at normal pressure, at a temperature lower than the boiling point of the main solvent, at a pressure higher than the boiling point of the main solvent, disclosed in JP-A-9-95544, JP-A-9-95557, Alternatively, various dissolution methods such as a cooling method as described in JP-A-9-95538 and a high-pressure method as described in JP-A-11-21379 can be used. A method in which pressure is applied at a boiling point or higher is preferred.

After adding or dissolving in the dope during or after dissolution, the dope is dissolved and dispersed, filtered through a filter medium, defoamed, and sent to the next process with a liquid feed pump.

For the filtration, it is preferable to use a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

FIG. 1 is a diagram schematically showing a dope preparation step, a casting step and a drying step of a solution casting film forming method preferable for the present invention.

If necessary, large aggregates are removed with a filter 44 from the acrylic particle charging vessel 41 and fed to the stock vessel 42. Thereafter, the acrylic particle additive solution is added from the stock kettle 42 to the main dope dissolving kettle 1.

Thereafter, the main dope solution is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added in-line from 16 to this.

In many cases, the main dope may contain about 10 to 50% by weight of recycled material. The return material may contain acrylic particles. In that case, it is preferable to control the addition amount of the acrylic particle addition liquid in accordance with the addition amount of the return material.

Recycled material is a finely pulverized acrylic film, which is generated when the acrylic film is formed, and is cut off on both sides of the film, or the original acrylic film that has been speculated out of scratches is used. .

Also, it is possible to preferably use a pellet obtained by kneading the acrylic resin (A), the acrylic particles (C), and optionally the cellulose ester resin (B).

2) Casting process An endless metal belt 31, such as a stainless steel belt, or a rotating metal drum, which feeds the dope through a liquid feed pump (for example, a pressurized metering gear pump) to the pressure die 30 and transfers it indefinitely. This is a step of casting the dope from the pressure die slit to the casting position on the support.

¡Pressure dies that can adjust the slit shape of the die base and make the film thickness uniform are preferred. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface.

In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and overlaid. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation process A web (dope is cast on a casting support, and the formed dope film is called a web) is heated on the casting support to evaporate the solvent to produce a film shape. It is a process.

To evaporate the solvent, there are a method in which air is blown from the web side, a method in which heat is transferred from the back surface of the support by a liquid, a method in which heat is transferred from the front and back by radiant heat, and the like. Well preferred. A method of combining them is also preferably used.

The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or heat by means such as infrared rays.

From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

The temperature at the peeling position on the metal support is preferably 10 to 40 ° C, more preferably 11 to 30 ° C.

The amount of residual solvent at the time of peeling of the web on the metal support at the time of peeling is preferably 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. When peeling at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be lost, or slippage and vertical stripes due to the peeling tension are likely to occur, so the balance between economic speed and quality The amount of residual solvent is determined.

The amount of residual solvent of the web that is the residual solvent of the present invention is defined by the following formula.

Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 140 ° C. for 2 hours.

The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m. However, if wrinkles easily occur at the time of peeling, it is preferable to peel with a tension of 190 N / m or less. It is preferable to peel at a minimum tension of ˜166.6 N / m, and then peel at a minimum tension of ˜137.2 N / m, and particularly preferable to peel at a minimum tension of ˜100 N / m.

In the present invention, the temperature at the peeling position on the metal support is preferably −50 to 40 ° C., more preferably 10 to 40 ° C., and most preferably 15 to 30 ° C.

5) Drying process After peeling, the web is transferred using a drying device 35 that alternately passes the web through rolls arranged in the drying device, or a tenter stretching device 34 that clips and transports both ends of the web with clips. dry.

The drying means is generally to blow hot air on both sides of the web, but there is also a means to heat by applying microwaves instead of wind. Too rapid drying tends to impair the flatness of the finished film.

It is preferable that the whole is dried at 40 to 160 ° C., and the residual solvent is adjusted to 5 to 50% by mass in this step.

6) Stretching step In the present invention, the stretching step is started in the state where the residual solvent is adjusted in the range of 1.0 to 100% in the above step.

When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

It is also preferable to provide a neutral zone between different temperature zones so that each zone does not cause interference.

The stretching operation may be performed in multiple stages, and it is also preferable to perform biaxial stretching in the casting direction and the width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting while relaxing the other tension.

The stretching ratio in the width direction is 1.2 to 2.0 times, and the stretching ratio in the longitudinal direction is 0.95 to 1.1 times.

The maximum stress during stretching is 10 to 400 kgf / m ² , the stretching temperature is apparent glass transition temperature (hereinafter referred to as apparent Tg) +10 to + 90 ° C., specifically 80 to 160 ° C., stretching speed 0.6 to 20 mm / Sec.

Here, the apparent Tg indicates a state in which a phenomenon such as softening occurs at a temperature lower than the actual glass transition temperature by including a solvent. Specifically, it can be measured by the following procedure.

In the fully dried acrylic film of the present invention (residual solvent amount less than 1% by mass), using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer) in advance in an atmosphere of 23 ° C. and 55% RH The sample conditioned for 24 hours is measured in a nitrogen stream at a heating rate of 20 ° C./min, and the glass transition temperature (Tg) is determined according to JIS K7121 (1987).

Next, the elastic modulus of this film is measured at a temperature of at least 5 points (with an interval of 10 ° C. or more) from 30 ° C. to 100 ° C., and an approximate curve (calibration curve) is created. Furthermore, the elastic modulus of the acrylic film containing the residual solvent is measured at 30 ° C., and the value at this time is defined as Ea (GPa).

A temperature corresponding to Ea (GPa) is calculated from a calibration curve prepared in advance, and this value is Ta (° C.).

Finally, apparent Tg apparent Tg (° C.) = Tg−Ta (° C.) − 30 (° C.)
Can be obtained as

In the stretching process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film, and the temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C. is most preferable.

This stretching condition is the element of the invention that contributes most to achieving the transparency and brittleness of the acrylic film of the present invention.

7) Heat treatment step It is preferable to heat-treat the film whose residual solvent has been adjusted to 5 to 50% by mass in the drying step at an apparent Tg + 10 to 90 ° C., and further to treat at an apparent Tg + 40 to 90 ° C. preferable. Specifically, the temperature is 80 to 160 ° C.

As a treatment method, the treatment may be performed in stages, such as treatment at about 120 ° C. at the beginning and heating at 140 ° C. at the end.

The heat treatment time is preferably 15 to 60 minutes, particularly preferably 20 to 40 minutes.

In this heat treatment step, drying is also performed at the same time, and it is preferable that the residual solvent amount of the acrylic film exiting from this step is less than 1.0% by mass.

8) Winding step This is a step of winding up the acrylic film by the winder 37 after the residual solvent amount in the web is 2% by mass or less, and the dimensional stability is achieved by setting the residual solvent amount to 0.4% by mass or less. A film having good properties can be obtained.

As a winding method, a generally used one may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc., and these may be used properly.

The acrylic film of the present invention is preferably a long film. Specifically, the acrylic film has a thickness of about 100 m to 5000 m and is usually provided in a roll shape. Further, the width of the film is preferably 1.3 to 4 m, more preferably 1.8 to 4 m.

The thickness of the acrylic film of the present invention is not particularly limited, but when used for the polarizing plate protective film described later, it is preferably 20 to 200 μm, more preferably 25 to 100 μm, and 30 to 80 μm. It is particularly preferred.
<Physical properties of acrylic film>
Hereafter, the characteristic about the physical property etc. of the acrylic film of this invention is demonstrated.

<Photoelastic coefficient>
The acrylic film of the present invention is preferably adjusted so that the photoelastic coefficient is −6.0 × 10 ⁻¹² to 6.0 × 10 ⁻¹² / Pa, and −2.0 × 10 ⁻¹² to 2. It is particularly preferable to control within the range of 0 × 10 ⁻¹² / Pa.

In the present invention, in order to adjust the photoelastic coefficient within the above range, the ratio of the acrylic resin (A) to the cellulose ester resin (B) and other resins is adjusted, and the phase difference control agent is adjusted according to this resin ratio. This is done by adjusting the combination and the amount to be added to optimize the composition of the acrylic film.

Even if stress is applied to the retardation film when the liquid crystal display device is turned on for a long time by adjusting the photoelastic coefficient to such a range and the panel becomes high temperature or the surrounding atmosphere becomes high temperature and high humidity. The phase difference is less likely to occur and image unevenness can be reduced. Furthermore, image unevenness that occurs when used for a long time can also be reduced.

<Moisture permeability>
The acrylic film of the present invention is measured under conditions of a temperature of 40 ° C. and a humidity of 90% RH based on JIS Z 0208, and the moisture permeability value converted to a film thickness proportional to a film thickness of 60 μm is 50 to 600 g / m ² · 24 h. It is particularly preferably 200 to 450 g / m ² · 24 h.

When the acrylic film of the present invention is used for at least one of the polarizing plates, by setting the moisture permeability to the above range, even if the liquid crystal display device is used in a high humidity environment, light leakage and image quality due to deterioration of the polarizer are prevented. Polarizer with vapor that does not deteriorate, and is generated even when the liquid crystal display device is placed in a high temperature environment and is used outdoors with high illuminance and exposed to high heat by increasing the brightness of the backlight. Deterioration and deformation can be suppressed.

<Others>
The acrylic film of the present invention has a defect of 5 μm or more in diameter in the film plane of 1 piece / 10 cm square or less. More preferably, it is 0.5 piece / 10 cm square or less, more preferably 0.1 piece / 10 cm square or less.

Here, the diameter of the defect indicates the diameter when the defect is circular, and when it is not circular, the range of the defect is determined by observing with a microscope according to the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. When the defect is a change in the surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope.

In addition, when observing with reflected light, if the size of the defect is not clear, aluminum or platinum is vapor-deposited on the surface for observation.

In order to obtain a film having excellent quality expressed by such a defect frequency with high productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set drying conditions after rolling stepwise and to dry efficiently while suppressing foaming.

When the number of defects is more than 1/10 cm square, for example, when a tension is applied to the film during processing in a later process, the film breaks with the defect as a starting point, and the productivity may be significantly reduced. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

Also, even when visual confirmation is not possible, when a hard coat layer or the like is formed on the film, the coating agent may not be formed uniformly, resulting in defects (coating defects). Here, the defect is a void in the film (foaming defect) generated due to the rapid evaporation of the solvent in the drying process of the solution casting, a foreign matter in the film forming stock solution, or a foreign matter mixed in the film forming. This refers to foreign matter (foreign matter defect) in the film.

Further, the acrylic film of the present invention preferably has a breaking elongation in at least one direction of 10% or more, more preferably 20% or more in the measurement based on JIS-K7127-1999.

The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming.

The thickness of the acrylic film of the present invention is preferably 20 μm or more. More preferably, it is 30 μm or more.

The upper limit of the thickness is not particularly limited, but in the case of forming a film by a solution casting method, the upper limit is about 250 μm from the viewpoint of applicability, foaming, solvent drying, and the like. The thickness of the film can be appropriately selected depending on the application.

The acrylic film of the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more.

Also, the practical upper limit is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film.

Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roll, calender roll, drum, belt, coating substrate in solution casting, transport roll, etc.) during film formation. It is also effective to reduce the diffusion and reflection of light on the film surface by reducing the refractive index of the acrylic resin (A).

The acrylic film of the present invention is characterized by having a haze value (turbidity), which is one of the indices indicating transparency, of 1.0% or less. However, the luminance and contrast when incorporated in a liquid crystal display device are characteristic. From the point, it is preferably 0.5% or less.

In order to achieve such a haze value, it is effective to remove foreign substances in the polymer by high-precision filtration and reduce the diffusion of light inside the film.

Also, the smoothness of the surface is expressed as surface haze, and it is also effective to reduce the particle diameter and addition amount of the acrylic particles within the above range, or to reduce the surface roughness of the film contact portion during film formation.

The total light transmittance and haze value of the acrylic film are values measured according to JIS-K7361-1-1997 and JIS-K7136-2000.

The acrylic film of the present invention can be preferably used as an optical acrylic film as long as the above physical properties are satisfied.

(Polarizer)
The acrylic film of the present invention can be used as a polarizing plate protective film. The polarizing plate can be produced by a general method.

It is preferable that an adhesive layer is provided on the back side of the acrylic film of the present invention, and is bonded to at least one surface of a polarizer produced by immersion and stretching in an iodine solution.

The film may be used on the other surface, or another polarizing plate protective film may be used. For example, commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KV8UY-HA, KV8UX-RHA, KV8UX-RHA Etc.) are preferably used.

A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

The polarizer is formed by forming a polyvinyl alcohol aqueous solution into a film and dyeing the film by uniaxial stretching or dyeing or uniaxially stretching, and then performing a durability treatment with a boron compound.

As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer, a pressure-sensitive adhesive having a storage elastic modulus at 25 ° C. in the range of 1.0 × 10 ⁴ Pa to 1.0 × 10 ⁹ Pa in at least a part of the pressure-sensitive adhesive layer is used. It is preferable to use a curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded.

Specific examples include, for example, urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, polyether methacrylate types, Examples include anaerobic pressure-sensitive adhesives such as ester-based methacrylate type and oxidized polyether methacrylate, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-component instantaneous pressure-sensitive adhesives.

The above-mentioned pressure-sensitive adhesive may be a one-component type or a type in which two or more components are mixed before use.

The above-mentioned pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The concentration of the pressure-sensitive adhesive liquid may be appropriately determined depending on the film thickness after adhesion, the coating method, the coating conditions, and the like, and is usually 0.1 to 50% by mass.

(Liquid crystal display device)
By incorporating the polarizing plate bonded with the acrylic film of the present invention into a liquid crystal display device using at least one surface of the liquid crystal cell, liquid crystal display devices having various durability can be manufactured. The polarizing plate of the present invention is bonded to a liquid crystal cell via the adhesive layer or the like.

The polarizing plate of the present invention is preferably a reflective, transmissive, transflective LCD or TN, STN, OCB, HAN, VA (PVA, MVA), IPS, etc. Used.

Example 1
[Preparation of acrylic resin]
The following acrylic resins A1-A7 and MS1,2 were prepared by known methods.

A1: Monomer mass ratio (MMA: MA = 98: 2), Mw 70000
A2: monomer mass ratio (MMA: MA = 97: 3), Mw 160000
A3: monomer mass ratio (MMA: MA = 97: 3), Mw350,000
A4: monomer mass ratio (MMA: MA = 97: 3), Mw550,000
A5: monomer mass ratio (MMA: MA = 97: 3), Mw 800000
A6: monomer mass ratio (MMA: MA = 97: 3), Mw 930,000
A7: monomer mass ratio (MMA: MA = 94: 6), Mw1100000
MS1: monomer mass ratio (MMA: ST = 60: 40), Mw100,000
MS2: monomer mass ratio (MMA: ST = 40: 60), Mw100,000
MMA: Methyl methacrylate MA: Methyl acrylate ST: Styrene (Synthesis of A8)
First, a methyl methacrylate / acrylamide copolymer suspension was prepared as follows.

Methyl methacrylate 20 parts by weight Acrylamide 80 parts by weight Potassium persulfate 0.3 part by weight Ion-exchanged water 1500 parts by weight The above is charged into the reactor and the reactor is replaced with nitrogen gas. The reaction was allowed to proceed at 70 ° C. until converted to. The obtained aqueous solution was used as a suspending agent. A solution in which 0.05 part by mass of the above suspending agent is dissolved in 165 parts by mass of ion-exchanged water is supplied to a stainless steel autoclave having a capacity of 5 liters and equipped with a baffle and a foudra-type stirring blade, and the system is filled with nitrogen gas. It stirred at 400 rpm, replacing.

Next, a mixed substance having the following charge composition was added while stirring the reaction system.

Methacrylic acid 27 parts by weight Methyl methacrylate 73 parts by weight t-dodecyl mercaptan 1.2 parts by weight 2,2′-azobisisobutyronitrile 0.4 part by weight The temperature was raised to 70 ° C. and the internal temperature was 70 ° C. The time at which the polymerization was reached was set as the polymerization start time, and the polymerization was continued for 180 minutes.

Thereafter, the reaction system was cooled, the polymer was separated, washed, and dried according to the usual method to obtain a bead-shaped copolymer. The polymerization rate of this copolymer was 97%, and the weight average molecular weight was 130,000.

0.2% by mass of additive (NaOCH ₃ ) is blended in this copolymer, and 10 L of nitrogen is supplied from the hopper using a twin screw extruder (TEX30 (manufactured by Nippon Steel Co., Ltd., L / D = 44.5)). While purging with an amount of / min., An intramolecular cyclization reaction is performed at a screw speed of 100 rpm, a raw material supply rate of 5 kg / hour, and a cylinder temperature of 290 ° C. to produce pellets, which are then vacuum-dried at 80 ° C. for 8 hours for acrylic resin The weight average molecular weight (Mw) of acrylic resin A8 was 130,000, and Tg was 140 ° C.

In addition, the following commercially available acrylic resins were used.

Dianar BR80 (Mitsubishi Rayon Co., Ltd.) Mw95000
Dianar BR83 (Mitsubishi Rayon Co., Ltd.) Mw40000
Dianar BR85 (Mitsubishi Rayon Co., Ltd.) Mw280000
Dianar BR88 (manufactured by Mitsubishi Rayon Co., Ltd.) Mw 480000
80N (Asahi Kasei Chemicals Corporation) Mw100,000
The ratio of the MMA unit in the molecule in the commercially available acrylic resin was 90% by mass or more and 99% by mass or less.

[Production of optical film]
<Preparation of optical film 101>
(Dope solution composition 1)
Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) 70 parts by mass Cellulose ester (cellulose acetate propionate acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 200000) ) 30 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above composition was sufficiently dissolved while heating to prepare a dope solution.

(Acrylic film formation)
The produced dope liquid was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. The solvent was evaporated with a stainless steel band support until the amount of residual solvent reached 100% by mass, and the film was peeled off from the stainless steel band support at a temperature of 35 ° C. and a peeling tension of 162 N / m.

The peeled acrylic film was further dried, slit to 1.6 m width, and stretched 1.4 times. The stretching temperature was 120 ° C. (apparent glass transition temperature 105 ° C. + 15 ° C.), and the stretching speed was 5% / sec and 8 mm / sec. The residual solvent amount when starting stretching with a tenter was 10% by mass.

After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then drying was completed while transporting the drying zone at 120 ° C. and 140 ° C. with many rolls, slitting to 2.0 m width, and 10 mm width at both ends of the film. A knurling process having a height of 5 μm was performed, and the film was wound around a core having an initial tension of 220 N / m and a final tension of 110 N / m, and an inner diameter of 15.24 cm, to obtain an optical film 1 which was an acrylic film.

The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.05.

The residual solvent amount of the optical film 101 shown in Table 1 was 0.1% by mass, the film thickness was 60 μm, and the winding length was 4000 m.

<Preparation of optical films 102-120>
Optical films 102 to 114 were prepared in the same manner as in the production of the optical film 101 except that the types and composition ratios of the acrylic resin (A) and the cellulose ester resin (B) were changed as shown in Table 1. . The film thickness was all 60 μm.

As the optical film 115, a film according to the film described in Example 3 of JP-A-2008-88417 was prepared. The stretching speed was 0.031% sec, and the stretching ratio was doubled under the conditions of 0.5 mm / sec. The weight average molecular weight of Acrypet V is Mw = 105000.

As the optical film 116, a film similar to the film described in Example 3 of JP-A-2008-88417 was prepared. However, the draw ratio was 1.4 times.

As the optical film 117, a film conforming to the film described in Example 3 of JP-A-2008-88417 was prepared. However, the stretching speed was 1.4% under the conditions of 5% / sec and 8 mm / sec.

The optical film 118 was formed by forming the components described in Example 3 of JP-A-2008-88417 in the same manner as the optical film 101.

As the optical film 119, a film according to the film described in Example 2 of JP-A-5-119217 was prepared. The weight average molecular weight of cellulose butyrate is Mw = 40000.

The optical film 120 was formed by forming the components described in Example 2 of JP-A-5-119217 in the same manner as the optical film 101.

The acyl groups of the cellulose ester resins described in Tables 1 and 2 are: ac is an acetyl group, pr is a propionyl group, bu is a butyryl group, pen is a pentanoyl group, bz is a benzoyl group, hep is a heptanoyl group, and oct is an octanoyl group , Ph represents a phthalyl group.

"Evaluation methods"
The obtained optical films 101 to 120 were evaluated as follows.

(Maximum stress during stretching kgf / m ² )
The tension (kgf) applied to the tenter during stretching was measured, and the maximum tension was divided by the cross-sectional area perpendicular to the stretching direction.

(Haze: Transparency evaluation that greatly affects contrast)
A square side of 3.5 cm square is cut out at intervals of 5 cm from one end in the TD direction to the other end. Further, at an arbitrary position, 50 or more square sides of 3.5 cm square are cut out in the MD direction at intervals of 5 cm in the MD direction. The haze of all the square-side films produced above was measured using a haze meter NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), and an average value and a maximum value were obtained.

The table shows the gradual value of film thickness (μm).

(Thickness variation%)
Using an all-infrared type thickness measuring machine manufactured by EGS Co., Ltd., a film thickness of 5 m or more in the MD direction from one end to the other end in the width direction of the arbitrary position and the center of the width in the arbitrary position. Were measured, and the average value, maximum value, and fluctuation were determined.
(Variation) = (standard deviation) ÷ (average value)
(Measurement method of tear strength kgf / μm)
Under the conditions of 23 ° C. and 55% RH, the tear load of the Elmendorf method was determined according to JIS K 7128-1991 in both the film transport direction (MD direction) and the direction orthogonal to the transport direction (TD direction). The tear strength was measured with a light load tearing device manufactured by (1). The average value was taken as the tear strength of the present invention.
(Characteristic evaluation as a liquid crystal display device)
<Preparation of polarizing plate>
A polarizing plate using each optical film as a polarizing plate protective film was prepared as follows. A 120 μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched in the transport direction 5 times at 50 ° C. to produce a polarizer.

Next, the optical film 101 produced in Example 1 was subjected to a corona treatment using an acrylic adhesive on one side of the polarizer, and then bonded.

Furthermore, KC8UCR-5 manufactured by Konica Minolta Opto Co., Ltd., which is a retardation film subjected to alkali saponification treatment, was bonded to the other surface of the polarizer and dried to prepare a polarizing plate P1. Similarly, polarizing plates were produced using the optical films 101 to 120.

<Production of liquid crystal display device>
Each of the produced polarizing plates was used to evaluate the display characteristics of the optical film.

Remove the polarizing plates on both sides of the 32-inch TV AQ-32AD5 manufactured by Sharp Corporation in advance so that the KC8UCR-5 is on the glass surface side of the liquid crystal cell. The liquid crystal display devices were each fabricated by pasting so that the absorption axis was directed in the same direction as the polarizing plate that had been pasted in advance.

The screen unevenness of this liquid crystal display device was evaluated. The results are shown in Table 1.

(Screen unevenness)
After manufacturing the liquid crystal display device, the backlight is continuously turned on for 5 hours in an environment of a temperature of 23 ° C. and a humidity of 55% RH, and the entire black display state is visually observed in a dark room, and the screen unevenness is visually evaluated. did.
A: No unevenness is observed at all.
○: Some unevenness is observed in a dark room.
Δ: Unevenness is observed in a dark room.
X: Unevenness is observed even in a bright room.

As is clear from Table 2, the optical film of the present invention has excellent transparency and brittleness, and excellent display quality.

Example 2
Optical films 201 to 237 were produced by changing the production conditions of the optical film 101 of Example 1 as shown in Table 3 such as the draw ratio, the draw speed, the draw temperature, and the residual solvent during drawing.

The same evaluation as Example 1 was performed about the obtained optical film. The results are shown in Table 4.

As is apparent from Table 4, the optical film of the present invention has excellent transparency and brittleness, and excellent display quality.

Example 3
Optical films 301 to 333 were produced as shown in Table 5 by the same production method as that of the optical film 101 in Example 1. The same evaluation as Example 1 was performed with respect to the optical film. The results are shown in Table 6.

As is clear from Table 6, the optical film of the present invention has excellent transparency and brittleness, and excellent display quality.

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber charging pot 20 Merge pipe 21 Mixer 30 Die 31 Metal support 32 Web 33 Peeling position 34 Tenter device 35 Roll dryer 41 Particle charging vessel 42 Stock tank 43 Pump 44 Filter

Claims (3)

1. The acrylic resin (A) and the cellulose ester resin (B) are in a mass ratio of 95: 5 to 30:70, and the weight average molecular weight Mw of the acrylic resin (A) is 110,000 to 1000000, and the cellulose ester resin (B ) Having a weight average molecular weight Mw of 75,000 or more and 280000 or less, a total substitution degree (T) of the acyl group of 2.0 or more and 3.0 or less, and a substitution degree of the acyl group of 3 or more and 7 or less carbon atoms is 1. An optical film characterized by being 2 or more and 3.0 or less and having the following relationship.
   (1) Haze average value ≦ 0.0150 × d
   (2) Haze maximum value ≦ 0.0180 × d
   (D represents the film thickness μm of the optical film.)
2. The optical film according to claim 1, wherein 1.0 ≦ haze maximum value / haze average value ≦ 1.1.
3. 3. The optical film according to claim 1, wherein the width of the optical film is 1.8 to 4 m.

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